Processing Systems and Methods for Semiconductor Devices

ABSTRACT

Systems and methods for processing semiconductor devices are disclosed. A preferred embodiment comprises a processing system that includes providing a processing system including a first container and a second container fluidly coupled to the first container, the second container being adapted to receive and retain an overflow amount of a fluid from the first container, and disposing the fluid in the first container and a portion of the second container. The method includes providing at least one semiconductor device, disposing the at least one semiconductor device in the first container, and maintaining the fluid in the second container substantially to a first level while processing the at least one semiconductor device with the fluid.

This application is a divisional of patent application Ser. No.11/595,446, entitled “Processing Systems and Methods for SemiconductorDevices,” filed on Nov. 9, 2006, which application is incorporatedherein by reference.

TECHNICAL FIELD

The present invention relates generally to semiconductor devices, andmore particularly to processing systems and methods used in themanufacturing of semiconductor devices.

BACKGROUND

Generally, semiconductor devices are used in a variety of electronicapplications, such as computers, cellular phones, personal computingdevices, and many other applications. Home, industrial, and automotivedevices that in the past comprised only mechanical components now haveelectronic parts that require semiconductor devices, for example.

Semiconductor devices are manufactured by depositing many differenttypes of material layers over a semiconductor workpiece, wafer, orsubstrate, and patterning the various material layers using lithography.The material layers typically comprise thin films of conductive,semiconductive, and insulating materials that are patterned and etchedusing lithography to form integrated circuits (ICs). There may be aplurality of transistors, memory devices, switches, conductive lines,diodes, capacitors, logic circuits, and other electronic componentsformed on a single die or chip, for example.

Lithography is a process in which a layer of photosensitive material isdeposited over a material layer, and the layer of photosensitivematerial is patterned by exposing the layer of photosensitive materialto energy through a lithography mask. The layer of photosensitivematerial is then developed, and the layer of photosensitive material isused as a mask while exposed portions of the material layer are etchedaway.

Dry etch techniques such as physical sputtering, ion beam milling,reactive ion etch (RIE), and plasma etch processes are often used topattern material layers of semiconductor devices, for example. However,some material layers in semiconductor devices, such as nitride layers,as an example, are often etched or removed using wet etch processes.

In a wet etch process, typically a semiconductor wafer or batch ofsemiconductor wafers are submerged in an etching liquid during an etchprocess. However, in some applications and with some wet etchchemistries, it can be difficult to control the etch rate.

Thus, what are needed in the art are improved wet etch processes andprocessing systems.

SUMMARY OF THE INVENTION

These and other problems are generally solved or circumvented, andtechnical advantages are generally achieved, by preferred embodiments ofthe present invention, which provide novel processing systems andmethods for semiconductor devices.

In accordance with a preferred embodiment of the present invention, aprocessing system includes providing a processing system including afirst container and a second container fluidly coupled to the firstcontainer, the second container being adapted to receive and retain anoverflow amount of a fluid from the first container. The fluid isdisposed in the first container and a portion of the second container.At least one semiconductor device is provided, and the at least onesemiconductor device is disposed in the first container. The fluid inthe second container is maintained substantially to a first level whileprocessing the at least one semiconductor device with the fluid.

The foregoing has outlined rather broadly the features and technicaladvantages of embodiments of the present invention in order that thedetailed description of the invention that follows may be betterunderstood. Additional features and advantages of embodiments of theinvention will be described hereinafter, which form the subject of theclaims of the invention. It should be appreciated by those skilled inthe art that the conception and specific embodiments disclosed may bereadily utilized as a basis for modifying or designing other structuresor processes for carrying out the same purposes of the presentinvention. It should also be realized by those skilled in the art thatsuch equivalent constructions do not depart from the spirit and scope ofthe invention as set forth in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention, and theadvantages thereof, reference is now made to the following descriptionstaken in conjunction with the accompanying drawings, in which:

FIG. 1 shows a system for processing semiconductor devices in accordancewith a preferred embodiment of the present invention that includes afluid container and a weir disposed proximate at least a portion of aperimeter of the fluid container;

FIG. 2 is a graph illustrating concentration fluctuations of the fluidthat may be caused by fluctuations in the fluid level in the weir;

FIG. 3 is a top view of the fluid container and the weir shown in FIG.1;

FIG. 4 shows a side view of the fluid container and the weir,illustrating some dimensions within the weir;

FIG. 5 shows another side view of the fluid container and the weir,illustrating the positioning of fluid level sensors in the weir inaccordance with a preferred embodiment of the present invention;

FIG. 6 is a graph showing that substantially constant concentrationlevels of the fluid achieved by maintaining a relatively constant fluidlevel in the weir result in a substantially constant etch rate inaccordance with a preferred embodiment of the present invention;

FIG. 7 shows a cross-sectional view of a semiconductor device having alayer of photosensitive material disposed over a material layer to bepatterned;

FIG. 8 shows the semiconductor device of FIG. 7 after a portion of thematerial layer has been etched using the novel processing systems andmethods of embodiments of the present invention;

FIG. 9 shows a cross-sectional view of a semiconductor device inaccordance with another embodiment of the present invention, wherein afirst material layer comprises a hard mask that is used to pattern anunderlying second material layer; and

FIG. 10 shows the semiconductor device of FIG. 9 after the hard mask hasbeen removed using the novel processing system and methods ofembodiments of the present invention.

Corresponding numerals and symbols in the different figures generallyrefer to corresponding parts unless otherwise indicated. The figures aredrawn to clearly illustrate the relevant aspects of the preferredembodiments and are not necessarily drawn to scale.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The making and using of the presently preferred embodiments arediscussed in detail below. It should be appreciated, however, that thepresent invention provides many applicable inventive concepts that canbe embodied in a wide variety of specific contexts. The specificembodiments discussed are merely illustrative of specific ways to makeand use the invention, and do not limit the scope of the invention.

The present invention will be described with respect to preferredembodiments in a specific context, namely implemented in processingtanks where a phosphoric acid (H₃PO₄) solution is used as a wet etchingfluid to pattern or remove nitride material layers, such as layers ofsilicon nitride (Si_(x)N_(y)). Embodiments of the present invention mayalso be applied, however, to other wet etch processing systems andsystems used to pattern, remove, or affect other types of materiallayers using other chemistries and etching solutions, for example.

H₃PO₄ etch processes are used in some semiconductor applications, e.g.,in state of the art technologies, such as in a 65 nm node architecture,as an example, in order to remove nitride layers. In H₃PO₄ etchprocesses, semiconductor wafers are submerged in a solution of H₃PO₄ anddeionized water in recirculated tanks. However, nitride etch ratesprocessed in H₃PO₄ tanks tend to show large variations in the etch rateover the bath lifetime. Maintaining a constant etch rate in an H₃PO₄process is challenging. The concentration of H₃PO₄ in an etching fluidaffects the etch rate: a high concentration of H₃PO₄ leads to a low etchrate, and a low concentration of H₃PO₄ results in a higher etch rate.Because the deionized water and/or the H₃PO₄ in the etching solutiontend to evaporate over time, which changes the H₃PO₄ concentration,deionized water is typically “spiked” or added into the tank on aperiodic basis or when the etch rate is observed to become too high inorder to maintain a constant concentration. However, adding deionizedwater to the bath requires complicated tool software and causes adifficult start up of the tool.

Changes in the etch rate of H₃PO₄ solutions over time result invariations in material thicknesses and etch times from lot to lot ofsemiconductor wafers, which is undesirable. Thus, what are needed aremethods of maintaining a stable concentration of H₃PO₄ in H₃PO₄ etchingsolutions, fluids, and systems.

Embodiments of the present invention achieve technical advantages bystabilizing the nitride etch rate in a recirculated hot H₃PO₄ bath. Thefluid level in a weir or overflow tank is retained at a constant level,so that the exposed surfaces from which deionized water and H₃PO₄evaporate are kept at constant dimensions, resulting in a constant etchrate.

Embodiments of the invention may be implemented in a recirculated hotH₃PO₄ bath type of etching system. Embodiments of the present inventionmay also be implemented in fluid processing systems that utilize othertypes of etching fluids and processing fluids, for example. The systemsand methods described herein are implementable in hardware and/orsoftware of a processing system or tool, for example.

With reference now to FIG. 1, there is shown a system 100 for processingsemiconductor devices 110 in accordance with a preferred embodiment ofthe present invention. The system 100 is also referred to herein as aprocessing system or an etching system herein. The system 100 may alsobe referred to as a wet bench, for example.

The processing system 100 includes a fluid container 102 and a weir 104disposed proximate at least a portion of a perimeter of the fluidcontainer 102. The container 102 is also referred to as a firstcontainer herein, and the weir 104 is also referred to as a secondcontainer herein, for example. The container 102 is preferably disposedwithin the weir 104, as shown. The container 102 and the weir 104comprise tanks adapted to hold a fluid 112. The container 102 may have alower portion that slopes inwardly towards the bottom, for example. Thecontainer 102 and the weir 104 are preferably square or rectangular in atop view, although alternatively, the container 102 and weir 104 maycomprise other shapes, such as round or elliptical, as examples. Thecontainer 102 may be larger than the weir 104; for example, thecontainer 102 may be adapted to hold about 30 to 50 liters of a fluid112, and the weir 104 may be adapted to hold about 5 liters or less of afluid 112, although alternatively, the container 102 and weir 104 maycomprise other sizes. The processing system 100 may include a lid thatcovers the top of both the container 102 and the weir 104, for example,not shown.

A support 106 for semiconductor devices 110, also referred to herein assemiconductor wafers 110, may be loaded with one or more semiconductordevices 110 and may be placed in the container 102 for processing in thefluid 112, as shown. The support 106 may comprise a cartridge orcarrier, for example, and may comprise legs or feet adapted to contactthe bottom of the container 102, as shown. The support 106 may compriseridges, recesses, or other shapes adapted to support and retain one ormore semiconductor wafers 110 during the processing of the semiconductorwafers 110 in the container 102, for example.

The fluid 112 preferably comprises an etch solution in some embodiments,although alternatively, the fluid 112 may comprise other fluids that maybe used to process the semiconductor devices 110, e.g., that may alteror affect the semiconductor device 110, for example. In a preferredembodiment, the fluid 112 comprises a solution of H₃PO₄ and deionizedwater. In some embodiments, the fluid 112 preferably comprises aconcentration of about 87 to 90% by weight of H₃PO₄ (at a predeterminedprocessing temperature) and about 13 to 10% by weight of deionizedwater, as an example, although alternatively, other concentrations ofH₃PO₄ and deionized water may also be used.

The fluid 112 is recirculated from the container 102 into the weir 104,then from an output port 122 of the weir 104 through a pipe 114 acoupled to the weir 104 to a pump 130 a, then through a pipe 114 bcoupled to the pump 130 a back to an input port 116 in a lower region,e.g., the bottom, of the container 102, as shown. Thus, the pump 130 arecirculates the fluid 112 from the weir 104 to the container 102 whilethe semiconductor devices 110 are processed in the container 102.

Additional fluid 112 may be added to the container 102 and/or the weir104 from a tank 126 containing a supply of a first fluid 134 and a tank128 containing a supply of a second fluid 136, for example. The firstfluid 134 may comprise deionized water and the second fluid 136 maycomprise H₃PO₄ in one embodiment, as examples, although alternatively,the first fluid 134 and the second fluid 136 may comprise other fluids.The first fluid 134 and the second fluid 136 preferably comprisecomponents of the solution of the fluid 112, for example.

At least one of the fluids 134 or 136 may be continuously added to thefluid 112, e.g., into the weir 104 and/or the container 102, during theetch process. For example, if the first fluid 134 comprises deionizedwater, the first fluid 134 may be added to the fluid 112 during an etchprocess at a constant rate of about 60 mL/min, in order to maintain astable concentration of the first fluid 134 and the second fluid 136 inthe fluid 112. However, advantageously, in accordance with embodimentsof the present invention, the first fluid 134 may not need to be addedto the fluid 112 during an etch process, to be described further herein.

Tank 128 may be coupled to the container 102 by a pipe 114 c coupled toa valve 132 a which is coupled to another pipe that enters into thecontainer 102. Tank 126 may be coupled by a pipe 114 d to a valve 132 bwhich is coupled to another pipe that enters into the container 102.Likewise, tank 128 may also be coupled by a pipe 114 e to a pump 130 bthat is coupled to another pipe 114 f that enters into the weir 104 atan input port 120 a to the weir 104, and tank 126 may be coupled by apipe 114 g to a pump 130 c that is coupled to another pipe 114 h thatenters into the weir 104 at an input port 120 b to the weir 104, asshown. Valves 132 a and 132 b or pumps 130 a, 130 b, and 130 c may beused to supply the fluids 134 and 136, depending on the location of thetanks 126 and 128 relative to the container 102 and weir 104; forexample, if the tanks 126 and 128 are positioned higher than thecontainer 102 and weir 104, then a pump 130 a, 130 b, and 130 c may notbe required, and a valve 132 a and 132 b may be used, utilizing gravityfor the movement of the fluids 112, 134, and 136.

The tanks 126 and 128, pumps 130 a, 130 b, and 130 c, valves 132 a and132 b, and pipes 114 a, 114 b, 114 c, 114 d, 114 e, 114 f, 114 g, and114 h may comprise a fluid delivery means, for example, coupled to thecontainer 102 and/or the weir 104 that is adapted to increase ordecrease the amount of fluid 112 in the container 102 and/or the weir104, and to also alter the concentrations of the first fluid 134 and/orthe second fluid 136 in the fluid 112 which comprises a solution of thefirst fluid 134 and the second fluid 136, for example.

The weir 104 is adapted to receive and retain an overflow amount of afluid 112 from the container 102. For example, the container 102 maycomprise sidewalls 138 and a top edge 118. The sidewalls 138 are alsoreferred to herein as a first vertical portion of the container 102 orfirst container. The weir 104 may comprise sidewalls 142 having a heightthat is greater than a height of the top edge 118 of the container 102.The sidewalls 142 are also referred to herein as a second verticalportion of the weir 104 or second container. The first vertical portion138 of the first container 102 comprises a top edge 118 that is lowerthan a top edge of the second vertical portion 142 of the secondcontainer 104. The weir 103 contains the fluid 112 within the inner edge144 of sidewalls 142 and within the outer edge 140 of sidewalls 138, forexample.

Thus, the second container 104 or weir is fluidly coupled to the firstcontainer 102 by the first vertical portion 138 of the first container102. If the level of the fluid 112 in the container 102 exceeds the topedge 118 of the sidewalls 138 of the container 102, the fluid 112 flowsover the top edge 118 and along the sidewalls 138 of the container 102into the weir 104, so that the fluid 112 covers the outer edge 140 ofsidewalls 138.

The processing system 100 may include a heater (not shown) coupled tothe fluid 112, 134, or 136, e.g., in the container 102, in the weir 104,coupled to a pipe 114 a, 114 b, 114 c, 114 d, 114 e, 114 f, 114 g, and114 h, and/or in the tanks 126 or 128. Preferably, during processing ofsemiconductor devices 110, the temperature of the fluid 112 ismaintained at about 155 to 165 degrees C.; e.g., in an embodimentwherein the fluid 112 comprises a solution of H₃PO₄ and deionized water,although alternatively, other temperatures may also be used. Thetemperature of the fluid 112 may be maintained at a temperature of about180 degrees C. or less in some embodiments, for example. The processingsystem 100 may also comprise a thermostat (also not shown) formonitoring and controlling the temperature of the fluid 112, forexample, not shown. The processing system 100 may also comprise one ormore filters (not shown) coupled within or to the fluid delivery means,to filter the fluids 112, 134, or 136, for example.

The processing system 100 may include a minimum level sensor 146disposed proximate a lower region of the weir 104, a full sensor 148disposed proximate a top edge of the container 102 within the weir 104,and an alarm sensor 150 disposed proximate the top edge of the sidewall142 of the weir 104, as shown. In accordance with an embodiment of thepresent invention, an additional sensor 152 may be disposed above thefull sensor 148, for example. The additional sensor 152 may comprise anoverfull sensor 152, for example, to be described further herein. One ormore of the sensors 146, 148, 150, or 152 may comprise a controllerdisposed in the second container or weir 104, wherein the controller146, 148, 150, or 152 is adapted to maintain the fluid 112 to asubstantially constant level in the second container 104 while at leastone semiconductor device and the fluid are contained within the firstcontainer. The controller 146, 148, 150, or 152 comprises at least onesensor 146, 148, 150, or 152 disposed proximate the level of thesubstantially constant level in the second container or weir 104, forexample.

The processing system 100 may also include a processor 151 that maycomprise a computer, as an example, and also may include software 154that may comprise code stored in a memory or other storage means, forexample. Embodiments of the present invention may comprise instructionsin the software 154 that are implementable, e.g., communicated to thevarious components of the system 100 by the processor 151, for example.

There are several factors that influence the concentration of the fluids134 and 136 in the fluid 112, which in turn influences the etch rate ofthe fluid 112. Factors that influence the concentration include thetemperature, the pressure, and the amount of fluids 134 and 136 added tothe fluid 112, as examples.

A heretofore unknown factor that further influences the concentration ofthe fluid 112 is the level of the fluid 112 in the weir 104. Inaccordance with preferred embodiments of the present invention, thelevel of the fluid 112 in the weir 104 is maintained at substantiallythe same predetermined level over time during an etch process, in orderto maintain a substantially constant concentration of the fluids 134 and136 in the fluid 112, resulting in a substantially constant etch rate,to be described further herein. For example, in some embodiments, thelevel of the fluid 112 in the weir 104 is preferably maintained at orbetween sensors 148 and 152, e.g., at a level substantially within arange represented by dimension d₁ in FIG. 1. In other embodiments, thelevel of the fluid 112 in the weir 104 is maintained substantially atthe level of the full sensor 148, for example.

The phenomenon of the fluid 112 level in the weir 104 affecting theconcentration of the fluids 134 and 136 that are components of thesolution of the fluid 112 will next be described. FIG. 2 is a graph 156illustrating experimental results of concentration fluctuations ofcomponents of a fluid 112 caused by fluctuations in the fluid 112 levelin a weir 104 where the fluid 112 comprised a solution of H₃PO₄ anddeionized water. Some concentration variations are observable in thegraph 156, the root cause for which was the changing of the fluid 112level in the weir 104, I discovered.

Referring again to FIG. 1, due to boiling and/or evaporation (e.g.,during heating) of the fluid 112 and due to removal of a portion of thefluid 112 when wafers 110 are removed to transfer them to a rinse tank(not shown) which may decrease the fluid 112 level to 155 or otherlevels, for example, there may be a steady decrease of the fluid 112level over the bath lifetime. Each time the carrier 106 supportingsemiconductor devices 110 is removed from the container 102, about ½ to1 liter of the fluid 112 is removed, for example. The level of the fluid112 in the container 102 is typically full during an etch process, e.g.,filling the entire dimension d₂ of the vertical portion of the container102, and the level in the container 102 may drop down by a dimension d₃when the wafers 110 are removed, for example. The level of the fluid 112in the weir 104 increases when additional wafers 110 are added to thecontainer 102, and the container 102 is then refilled with the fluid 112from the weir 104. Thus, the level of the fluid 112 in the weir 104decreases or drops down over time as batches of devices 110 areprocessed.

The graph 156 in FIG. 2 illustrates concentration changes that occurredwhen the minimum sensor 146 signal was lost. At that time, e.g., at timet₁, the concentration (c) by percentage of weight of H₃PO₄ in the fluid112 was about 88.0%. When the system 100 detected that the level of thefluid 112 had dropped below the minimum sensor 146 level, the system 100refilled the weir 104 up to the full sensor 148, e.g., with fluid 112from tanks 134 and 136, increasing the level of the fluid 112 in theweir 104 by a dimension d₄ along a sidewall 142 of the weir 104. Theconcentration by percentage of weight of H₃PO₄ in the fluid 112decreased after the level of the fluid 112 was increased in the weir 104from time t₁ to time t₂ to less than 87.0%. The weir 104 was thendrained to lower the fluid 112 level in the weir 104, resulting in anincrease in the concentration of H₃PO₄ in the fluid 112 to about 87.6%,as shown at time t₃ in graph 156. The concentration changes shown ingraph 156 correlate with the changes made to the fluid 112 level in theweir 104. Note that in the experimental results shown in FIG. 2, fluid134 was introduced at a constant rate to the fluid 112 in the weir 104;e.g., the deionized water “spiking” rate was held constant during theexperiment.

Fluid 112 level variations in the weir 104 result in a change in thesize of the fluid 112 surface areas. FIGS. 3 and 4 illustrate somedimensions of the fluid container 102 and the weir 104. FIG. 3 is a topview of the fluid container 102 and the weir 104 shown in FIG. 1, andFIG. 4 shows a side view of the fluid container 102 and the weir 104.

In the experimental results shown in the graph 156 of FIG. 2, theprocessing system 100 (see FIG. 3) comprised a first container 102comprising a width WP of 24.8 cm and a length LP of 42 cm. Theprocessing system 100 comprised a second container or weir 104comprising a width WW of 4.8 cm (e.g., the distance between thesidewalls 138 of the container 102 and the sidewalls 142 of the weir104), a length LW2 along one side of 51.6 cm, and a length LW1 alonganother side of 34.4 cm.

The surface area of the fluid 112 in the processing system 100 comprisedtwo components: the horizontal surface area and the vertical surfacearea. The horizontal surface area may be calculated by summing thesurface area of the container 102 and the surface area of the weir 104,as shown in Eq. 1:

horizontal surface area=(LP*WP)+(2*WP*WW)+(2*LW2*WW)  Eq. 1:

which results in a horizontal surface of 1,775 cm² for the example shownin FIG. 2.

The vertical surface area component results from the fluid 112 flowingdown the sidewalls 138 out of the container 102 into the weir 104, thuscreating an additional surface. The surface area of this verticalsurface depends strongly on the level of the fluid 112 in the weir 104.For example, in FIG. 4, which shows a side view of the fluid container102 and the weir 104, a first level, “level 1” and a second level,“level 2” are shown, wherein level 2 is greater than level 1. Thevertical surface area may be calculated using Equation 2:

vertical surface area=(2*LP*level X)+(2*WP*level X);  Eq. 2:

wherein level X=level 1 or level 2.

In the experimental results previously described with reference to FIG.2, the dimension level 1 was about 6 cm, and the dimension level 2 wasabout 22.5 cm: therefore, the vertical surface area calculated usinglevel 1 and Eq. 2 is 802 cm², whereas the vertical surface areacalculated using level 2 and Eq. 2 is 3,006 cm². Thus, this demonstratesthat the vertical surface area has a large impact on the overall surfacearea of the fluid 112.

If the fluid 112 level decreases in the weir 104, then the verticalsurface area increases, which increases the rate of evaporation of theacid (e.g., fluid 136) and deionized water (e.g., fluid 134) in thefluid 112, for example. Thus, in accordance with embodiments of thepresent invention, the fluid 112 level is preferably advantageously keptconstant in the weir 104 during an etch process. This is achieved insome embodiments by maintaining the level of the fluid 112 in the weir104 at a constant level, e.g., using an existing sensor, such as a fullsensor 148 within the weir 104, and by modifying software 154 (seeFIG. 1) of the processing system 100 to include instructions for theprocessor 151 to instruct other components of the system 100 to refillthe weir 104 when the full sensor 148 signal is lost. The full sensor148 signal may be observed more frequently, e.g., the time periodsbetween checking the full sensor 148 signal may be decreased, in thisembodiment.

The fluid 112 is preferably maintained at a relatively high level withinthe weir 104 in some embodiments while processing semiconductor devices110, e.g., the fluid 112 is preferably maintained at a level at overhalf to ⅔ full, in order to decrease the amount of evaporation of thecomponents 134 and 136 of the fluid 112, by minimizing the verticalsurface area of the fluid 112 flowing from the container 102 into theweir 104, as an example.

In other embodiments of the present invention, an additional sensor 152may be used for maintaining the fluid 112 in the weir 104 at a constantlevel. For example, an overfull sensor 152 may be included in the weir104 disposed above the full sensor 148 specifically for the purpose ofmaintaining the weir fluid 112 level. Each time the fluid 112 leveldrops below the full sensor 148, the fluid 112 in the weir 104 isrefilled until the full sensor 148 is reached again. In this embodiment,when the fluid 112 level rises and is detected by the overfull sensor152, which may occur when only a few wafers 110 are processed over aperiod of time, because the deionized water (e.g., fluid 134 in FIG. 1)continues to be added to the fluid 112 during the processing of thesemiconductor devices 110, the level of the overfull sensor 152 may bereached. Instructions are preferably included in the software 154 of theprocessing system 100 to instruct the weir 104 to be drained or forfluid 112 to be removed from the weir 104 until the fluid 112 levelwithin the weir 104 is decreased below the overfull sensor 152 level,for example, in this embodiment.

FIG. 5 shows another side view of the fluid container 102 and the weir104, illustrating the positioning of fluid level sensors 146, 148, 152,150 on the weir 104 in accordance with a preferred embodiment of thepresent invention. In accordance with embodiments of the presentinvention, the level of the fluid 112 is maintained as constant aspossible, because large differences in the fluid 112 level in the weir104 lead to large changes of the fluid 112 surface (e.g., the size ofthe vertical surface area of the fluid 112 flowing down sidewalls 138 ofthe container 102) that can lead to higher or lower evaporation of theacid (H₃PO₄), causing fluctuations in the concentration levels of theacid (e.g., fluid 136) and also the etch rate. Thus, fluctuations in theacid 136 of the fluid 112 are reduced or eliminated by embodiment of thepresent invention, resulting in a substantially constant etch rate.

For example, in the embodiment wherein an overfull sensor 152 isincluded above the full sensor 148, the fluid 112 level is preferablymaintained within the level d₁ between the overfull sensor 152 and thefull sensor 148. The overfull sensor 152 is preferably disposed about 5cm or less above the full sensor 148 in this embodiment, so that thevertical level of the fluid 112 does not fluctuate by more than about 5cm during processing of semiconductor devices 110. More preferably, forthe vertical level of the fluid 112 does not fluctuate by more thanabout 1 cm during processing of semiconductor devices 110, as anotherexample. Most preferably, for example, the vertical level of the fluid112 does not fluctuate or deviate at all during processing ofsemiconductor devices 110, in some embodiments. In the embodimentwherein an overfull sensor 152 is not included, the level in the weir104 is preferably maintained at or about the level where the full sensor148 is positioned, e.g., as shown in phantom at 153.

FIG. 6 is a graph showing that relatively constant concentration levelsof the fluid 112 in the weir 104 are achieved by maintaining arelatively constant fluid 112 level in the weir 104, shown in the graphat 158, resulting in a relatively constant etch rate in accordance withthe preferred embodiment of the present invention, as shown in the graphat 160. An example of an etch process using a fluid 112 comprising asolution of H₃PO₄ and deionized water to etch a nitride layer ofsemiconductor devices 110 is shown in FIG. 6. The results shown in FIG.6 were achieved by draining and refilling the fluid 112, maintaining asubstantially constant fluid 112 level within the weir 104 during theetch process. The deionized water “spiking” was also kept constant overthe entire time.

Preferably, the concentration of H₃PO₄ in the fluid 112 does not changeby more than about 0.5%, in accordance with embodiments of the presentinvention, and more preferably, the concentration of H₃PO₄ in the fluid112 does not change at all over time, for example. Also, preferably, theetch rate for etching material layers of semiconductor devices 110 doesnot change by more than 0.5 nm or less over time, and more preferably,the etch rate for etching material layers of semiconductor devices 110does not change at all over time during an etch process, in accordancewith embodiments of the present invention, for example.

Embodiments of the present invention also include methods of processingand manufacturing semiconductor devices 110, and semiconductor devices110 processed and manufactured using the methods and systems 100described herein.

FIG. 7 shows a cross-sectional view of a semiconductor device 110 havinga layer of photosensitive material 174 disposed over a material layer172 to be patterned, and FIG. 8 shows the semiconductor device 110 ofFIG. 7 after at least a portion of the material layer 172 has beenetched using the novel processing system 100 and methods of embodimentsof the present invention.

To manufacture the semiconductor device 110, first, a workpiece 170 isprovided. The workpiece 170 may include a semiconductor substratecomprising silicon or other semiconductor materials covered by aninsulating layer, for example. The workpiece 170 may also include otheractive components or circuits, not shown. The workpiece 170 may comprisesilicon oxide over single-crystal silicon, for example. The workpiece170 may include other conductive layers or other semiconductor elements,e.g., transistors, diodes, etc. Compound semiconductors, GaAs, InP,Si/Ge, or SiC, as examples, may be used in place of silicon. Theworkpiece 170 may comprise a silicon-on-insulator (SOI) substrate, forexample.

A material layer 172 is deposited or formed over the workpiece 170. Thematerial layer 172 preferably comprises a nitride material such assilicon nitride or silicon oxynitride (SiO_(x)N_(y)) in someembodiments, as examples, although the material layer 172 may compriseother materials, such as other insulating materials, conductors,semiconductive materials, or combinations thereof.

A layer of photosensitive material 174 may be deposited over thematerial layer 172. The layer of photosensitive material 174 may bepatterned using lithography, e.g., by exposing the layer ofphotosensitive material 174 to energy through a lithography mask, andthen the layer of photosensitive material 174 is developed, forming apattern, as shown in FIG. 7.

The semiconductor device 110 may then be placed in the container 102 tobe processed or affected by the fluid 112 for a predetermined period oftime, for example, as shown in FIG. 1. For example, a portion of thematerial layer 172 may be removed or etched, to a level d₅ below a topsurface of the material layer 172, as shown in FIG. 8. Or, the materiallayer 172 may be etched through its entirety until the top surface ofthe workpiece 102 is exposed, not shown, to completely pattern thematerial layer 172. The layer of photosensitive material 174 is thenremoved, and processing of the semiconductor device 110 is thencontinued.

FIG. 9 shows a cross-sectional view of a semiconductor device inaccordance with another embodiment of the present invention, wherein afirst material layer 172 comprises a hard mask, e.g., comprising anitride material, that is used to pattern an underlying second materiallayer 176. FIG. 10 shows the semiconductor device of FIG. 9 after thehard mask 172 has been removed using the novel processing system 100 andprocessing systems of embodiments of the present invention. For example,in a preferred embodiment, the material layer 172 to be affected by thefluid 112 may comprise a nitride material.

In this embodiment, the material layer 172 was used as a sacrificiallayer, such as a hard mask or for another purpose. After the workpiece170 is provided, a second material layer 176 is formed over theworkpiece 170 (note that the material layers are not numbered in orderof deposition in this embodiment), and the first material layer 172comprising the hard mask is deposited over the second material layer176. A layer of photosensitive material 174 is deposited over the firstmaterial layer 172 (not shown in FIG. 9; see FIG. 7). The layer ofphotosensitive material 174 is used as a mask to pattern the hard mask172. The layer of photosensitive material 174 may be removed or may beleft residing over the hard mask 172, not shown.

Then, the nitride material 172 is used as a hard mask to process anunderlying second material layer 176, or if the second material layer176 is not present, the nitride material 172 is used as a mask toprocess the workpiece 170 (not shown) of the semiconductor device 110.The second material layer 176 or workpiece 170 of the semiconductordevice 110 is affected or altered using the patterned nitride material172 as a hard mask.

For example, affecting or altering the underlying second material layer176 or the workpiece 170 of the semiconductor device 110 may compriseetching away at least a portion of the underlying second material layer176 or workpiece 170, as shown in FIG. 10. Alternatively, affecting oraltering the underlying second material layer 176 or the workpiece 170may comprise implanting dopants, impurities, or other substances intothe underlying second material layer 176 or workpiece 170; or forming ordepositing a material or substance over exposed portions of theunderlying second material layer 176 or workpiece 170 (not shown),although other alterations to the underlying second material layer 176or workpiece 170 may also be performed with the patterned nitridematerial 172 present.

Next, the semiconductor device 110 is placed in the container 102 withthe fluid 112 residing therein, and the first material layer or thenitride material 172, and any photosensitive material 174, if present,is partially or completely removed from over the underlying materiallayer or the workpiece 170. Thus, in this embodiment, processing thesemiconductor device 110 in the novel processing system 100 comprisesetching away all of the nitride material layer 172.

Advantageously, the etch rate from lot to lot of semiconductor devices110 is kept substantially constant, because from lot to lot ofprocessing semiconductor devices 110 using the processing system 100,the fluid 112 level in the weir 104 is maintained at substantially thesame level, e.g., either within dimension or range d₁, or substantiallyat level 148, as shown in FIG. 5, in accordance with preferredembodiments of the present invention.

Advantages of embodiments of the present invention include providingsystems 100 and methods of stabilizing the etch rate of wet etchprocesses. The methods may be implemented into the hardware and/orsoftware 154 of existing wet bench tools, for example. Complicatedsoftware is not required to implement embodiments of the presentinvention, and the start up of the tool or processing system 100 may beincreased or made faster. Furthermore, the reliability of the processingsystem 100 and processing systems in a production environment is higher,and more predictable etch times and results are achieved forsemiconductor devices 110.

In some embodiments, the need to add deionized water to the fluid 112during the etch process may be eliminated, by maintaining the fluid 112level within the weir 104. This results in less complicated software 154required in the system 100 and simplifies the start up of the processingsystem 100, for example.

Although embodiments of the present invention and their advantages havebeen described in detail, it should be understood that various changes,substitutions and alterations can be made herein without departing fromthe spirit and scope of the invention as defined by the appended claims.For example, it will be readily understood by those skilled in the artthat many of the features, functions, processes, and materials describedherein may be varied while remaining within the scope of the presentinvention. Moreover, the scope of the present application is notintended to be limited to the particular embodiments of the process,machine, manufacture, composition of matter, means, methods and stepsdescribed in the specification. As one of ordinary skill in the art willreadily appreciate from the disclosure of the present invention,processes, machines, manufacture, compositions of matter, means,methods, or steps, presently existing or later to be developed, thatperform substantially the same function or achieve substantially thesame result as the corresponding embodiments described herein may beutilized according to the present invention. Accordingly, the appendedclaims are intended to include within their scope such processes,machines, manufacture, compositions of matter, means, methods, or steps.

1. A processing system comprising: a first container, the firstcontainer being adapted to contain a fluid and a semiconductor device; asecond container fluidly coupled to the first container, the secondcontainer being adapted to receive and retain an overflow amount of afluid from the first container; and a controller, wherein, while thesemiconductor device and the fluid are contained within the firstcontainer, the controller is adapted to maintain the fluid to asubstantially constant level in the second container by continuouslyflowing the fluid on an outer vertical sidewall of the first containerthereby forming an evaporative vertical surface during an entireduration that the semiconductor device is contained in the firstcontainer, wherein the controller is adapted to maintain the continuousfluid flow by a continuous flow of deionized water into the firstcontainer during the entire duration that the semiconductor device iscontained in the first container, and maintaining a height of theevaporative vertical surface by maintaining the fluid in the secondcontainer, wherein the controller is adapted to maintain the height bykeeping the fluid between a first lower sensor and a second uppersensor, wherein the first lower and the second upper sensors are placedclose to an upper edge of the first container, and wherein thecontroller is adapted to maintain the evaporative vertical surface ismaintained during the entire duration that the semiconductor device iscontained in the first container.
 2. The processing system according toclaim 1, wherein the processing system further comprises at least oneheater, at least one pump, at least one thermostat, at least one valve,or at least one filter, coupled to the fluid.
 3. The processing systemaccording to claim 1, wherein the controller is configured to maintainthe fluid in the second container by adding additional fluid from afluid supply tank to the first container if the fluid is reduced belowthe first lower sensor.
 4. The processing system according to claim 3,wherein the controller is configured to add the additional fluid to thefirst or second container until the first lower sensor detects thefluid.
 5. The processing system according to claim 3, wherein thecontroller monitors the second upper sensor disposed in the secondcontainer and if the second upper sensor detects the fluid, thecontroller is configured to remove a portion of the fluid from thesecond container until the second upper sensor does not detect thefluid.
 6. The processing system according to claim 1, wherein the firstcontainer comprises a lower region and an upper region, wherein thelower region comprises tapered sidewalls, wherein an overfill sensor,the first lower sensor, and the second upper sensor are disposed on thesecond container and facing the upper region, and wherein a minimumlevel sensor is disposed on the second container and facing the lowerregion.
 7. The processing system according to claim 1, wherein the fluidcomprises a solution of H₃PO₄ and deionized water, and wherein thecontroller is configured to maintain a continuous flow of H₃PO₄ into thefirst container during the entire duration that the semiconductor deviceis disposed in the first container.
 8. The processing system accordingto claim 1, wherein a top edge of the outer vertical sidewall of thefirst container is lower then a top edge of an outer vertical sidewallof the second container.
 9. A processing system comprising: a firstcontainer configured to contain a fluid and a semiconductor device; aweir fluidly coupled to the first container, the first container beingdisposed within the weir, the weir comprising a second containerdisposed about a perimeter of the first container that is adapted toreceive and retain an overflow amount of the fluid from the firstcontainer; and a controller configured to completely fill the firstcontainer and partially fill the weir with the fluid, the controllerbeing configured to continuously flow the fluid on an outer verticalsidewall of the first container into the weir thereby forming anevaporative vertical surface, wherein the controller is furtherconfigured to maintain a height of the evaporative vertical surfaceformed by the continuous fluid flow during the entire time that thesemiconductor device is in the first container.
 10. The processingsystem according to claim 9, wherein the controller is configured tomaintain the height by maintaining the fluid in the weir substantiallyto a level close to a top edge of the first container while thesemiconductor device is contained in the first container, and whereinthe controller is configured to maintain the fluid in the weir to avertical distance on a sidewall of the weir over a range of about 5 cmor less.
 11. The processing system according to claim 9, wherein thefluid comprises an etching solution configured to etch a material layerof the semiconductor device.
 12. The processing system according toclaim 9, wherein the fluid comprises a solution of H₃PO₄ and deionizedwater, and wherein the controller is configured to maintain the fluid inthe weir by maintaining a predetermined concentration amount of theH₃PO₄ in the fluid.
 13. The processing system according to claim 12,wherein the controller is further configured to introduce deionizedwater to the fluid at a constant rate while the semiconductor device isin the first container.
 14. The processing system according to claim 9,wherein the first container comprises a lower region and an upperregion, wherein the lower region comprises tapered sidewalls, wherein anoverfill sensor, a first lower sensor, and a second upper sensor aredisposed on the weir and facing the upper region, and wherein a minimumlevel sensor is disposed on the weir facing the lower region.
 15. Theprocessing system according to claim 9, wherein the fluid comprises asolution of H₃PO₄ and deionized water, and wherein the controllermaintains a continuous flow of H₃PO₄ into the first container during theentire duration that the semiconductor device is disposed in the firstcontainer.
 16. A processing system comprising: a first container adaptedto contain a fluid and a semiconductor device; a weir fluidly coupled tothe first container, the first container being disposed within the weir,the weir comprising a second container disposed about a perimeter of thefirst container that is adapted to receive and retain an overflow amountof the fluid from the first container, wherein the fluid comprises asolution of H₃PO₄ and deionized water; and a controller configured tocompletely fill the first container and partially fill the weir with thefluid, wherein the controller is adapted to maintain a continuous flowof H₃PO₄ and deionized water into the first container during an entireduration that the semiconductor device is disposed in the firstcontainer, wherein the controller is further adapted to maintain acontinuous fluid flow on an outer vertical sidewall of the firstcontainer into the weir thereby forming an evaporative vertical surface,wherein the controller is adapted to maintain a height of theevaporative vertical surface formed by the continuous fluid flow duringthe entire duration that the semiconductor device is disposed in thefirst container.
 17. The processing system according to claim 16,wherein the controller is configured to maintain the height bymaintaining the fluid in the weir substantially to a level close to atop edge of the first container while the semiconductor device iscontained in the first container, and wherein the controller is furtheradapted to maintain the fluid in the weir to a vertical distance on asidewall of the weir over a range of about 5 cm or less.
 18. An etchingsystem comprising: a container adapted to support a semiconductordevice; a weir fluidly coupled to the container, the container beingdisposed within the weir, the weir being disposed about at least aportion of a perimeter of the container, the weir being adapted toreceive and retain an overflow amount of an etching fluid from thecontainer; at least one sensor disposed within the weir, wherein asensor of the at least one sensors is adapted to monitor a level of theetching fluid within the weir; means for maintaining a height of anevaporative vertical surface formed by a continuous flow of the etchingfluid during an entire duration that the semiconductor device issupported in the container; means for obtaining information regardingthe level of the etching fluid within the weir from the at least onesensor; and means for altering the etching fluid level in accordancewith the information obtained, maintaining the etching fluid in the weirto a vertical level of a range of about 5 cm or less.
 19. The etchingsystem according to claim 18, wherein the at least one sensor comprisesa minimum level sensor, an alarm overfill sensor, and/or a full sensor.20. The etching system according to claim 18, wherein a sensor of the atleast one sensors comprises a full sensor adapted to monitor the levelof the etching fluid within the weir over the range of about 5 cm orless of a predetermined level.
 21. The etching system according to claim20, further comprising an overfull sensor disposed above the fullsensor.
 22. The etching system according to claim 18, further comprisinga pump adapted to dispose the etching fluid from the weir into thecontainer during an etching process for the semiconductor device.